Te-Ho Wu

• PhD
• Professor (Full) at National Yunlin University of Science and Technology

Here, we study the magnetic properties of compositionally varied TbCo films on Ta and Al seed layers. The anomalous Hall effect (AHE) and magnetization hysteresis (MH) results show the sperimagnetic behavior of Tb for both cases. Further, we introduced a vertical composition gradient in TbCo and measured their AHE and MH response. Ta-based film rev...

This study delves into the unique properties of the GdFeCo Hall bar with a vertical composition gradient. Our exploration includes a detailed analysis of the temperature-dependent extraordinary Hall effect (EHE) response and magnetization-switching behavior. The findings reveal a FeCo-rich state at room temperature, characterized by an asymmetric d...

Ferrimagnetic rare-earth (RE) – transition-metal (TM) alloys are considered small ferromagnets with antiferromagnetic exchange in sublattices, which makes them a preferable choice for future ultrafast memory-related applications. Here, we explore the magnetic properties of two GdFeCo thin films with tailored vertical composition gradients, achieved...

This study investigated the effects of varying film thicknesses and annealing temperatures on the surface roughness and magnetic domain structure of CoFeSm thin films. The results revealed that as the film thickness increased, both the crystalline size and surface roughness decreased, leading to a reduction in coercivity (Hc) and improved magnetic...

Although it is not a medical diagnosis, brain fog composes of sluggish or fuzzy thinking, impaired memory, confusion, and difficulty in focus. In general, this can be caused by stress, sleep disorder, or other illnesses. After the outbreak of COVID-19, an increasing number of patients suffer from COVID-19 brain fog. Since the symptoms of brain fog...

A typical body-centered cubic (BCC) CoFe(110) peak was discovered at approximately 2θ = 44.7°. At 2θ = 46°, 46.3°, 47.7°, 55.4°, 54.6°, and 56.4°, the Yb2O3 and Co2O3 oxide peaks were visible in all samples. However, with a heat treatment temperature of 300 °C, there was no typical peak of CoFe(110). Electrical characteristics demonstrated that res...

The aim of this work is to investigate the effect of annealing and thickness on various physical properties in Co40Fe40Yb20 thin films. X-ray diffraction (XRD) was used to determine the amorphous structure of Co40Fe40Yb20 films. The maximum surface energy of 40 nm thin films at 300 °C is 34.54 mJ/mm². The transmittance and resistivity decreased sig...

The race-track memory concept relies on domain wall propagation through a magnetic track, which has the potential to change the future course of memory-related applications. Therefore, the materials where one can control the propagation of domain walls are crucial. Further, the stochastic nature of magnetization switching has potential applications...

It is commonly known that the coercivity (H c ) of the rare-earth/transition-metal (RE–TM) compound is tuned based on the varying RE content as compared to the TM component. The drawback of this approach is that the H c changes are permanent. In this work, we investigate the coercivity behaviors of the GdFeCo/Hf/MgO heterostructure where the heavy...

X-ray diffraction indicated an amorphous state of all annealed films, indicating that boron in CoFeW films could refine grain size and low annealing temperatures did not induce sufficient thermal driving force to support grain growth. The saturation magnetization (Ms) and low-frequency alternate-current magnetic susceptibility (χac) increased with...

Here we report the influence of deposition parameters on the magnetic properties of Hf/Gd-Fe-Co sheet films. Samples were grown in a magnetron sputtering where the target’s power, pre-sputtering time and power, and capping layer were varied to find the stable perpendicular magnetic anisotropy (PMA) in the series. The magnetic properties of the shee...

Here we report the influence of deposition parameters on the magnetic properties of Hf/Gd-Fe-Co sheet films. The magnetic properties are studied by anomalous Hall effect measurements. Samples were grown in a magnetron sputtering where the target’s power, pre-sputtering time and power, and capping layer are changed to find the stable perpendicular m...

We present a powerful method to detect the magnetic domain wall (DW), based on the intrinsic characteristic of anomalous Hall effect (AHE), by employing magneto-transport measurement on a device of double Hall cross geometry. We demonstrate that DW propagation manifests its behavior in the distinctive AHE hysteresis and longitudinal magnetoresistan...

Co60Fe20Y20 film was sputtered on glass substrate with a 10 nm to 50 nm under four annealed conditions and the structure, magnetic properties, surface energy, and optical property were examined. An amorphous structure of CoFeY films was revealed by an X-ray diffraction analyzer, suggesting that the addition of yttrium (Y) refined the grain size and...

This study investigated Co40Fe40W20 single-layer thin films according to their corresponding structure, grain size, contact angle, and surface energy characteristics. Co40Fe40W20 alloy thin films of different thicknesses, ranging from 10 to 50 nm, were sputtered on Si(100) substrates by DC magnetron sputtering. The thin films were annealed under th...

This research explores the behavior of Co40Fe40W10B10 when it is sputtered onto Si(100) substrates with a thickness (tf) ranging from 10 nm to 100 nm, and then altered by an annealing process at temperatures of 200 °C, 250 °C, 300 °C, and 350 °C, respectively. The crystal structure and grain size of Co40Fe40W10B10 films with different thicknesses a...

In this paper, a Co60Fe20Y20 film was sputtered onto Si (100) substrates with thicknesses ranging from 10 to 50 nm under four conditions to investigate the structure, magnetic properties, and surface energy. Under four conditions, the crystal structure of the CoFeY films was found to be amorphous by an X-ray diffraction analyzer (XRD), suggesting t...

Here we investigate the temperature dependence of anomalous Hall effect in Hf/GdFeCo/MgO sheet film and Hall bar device. The magnetic compensation temperature (Tcomp) for the sheet film and device is found to be ~240 K and ~118 K, respectively. In sheet film, spin-flopping is witnessed at a considerably lower field, 0.6 T, close to Tcomp. The AHE h...

Co40Fe40W20 monolayers of different thicknesses were deposited on Si(100) substrates by DC magnetron sputtering, with Co40Fe40W20 thicknesses from 10 to 50 nm. Co40Fe40W20 thin films were annealed at three conditions (as-deposited, 250 °C, and 350 °C) for 1 h. The structural and magnetic properties were then examined by X-ray diffraction (XRD), low...

Here we investigate the temperature dependence of anomalous Hall effect in Hf/GdFeCo/MgO sheet film and Hall bar device. The magnetic compensation temperature (Tcomp) for the sheet film and device is found to be ~240 K and ~118 K, respectively. In sheet film, spin-flopping is witnessed at a considerably lower field, 0.6 T, close to Tcomp. The AHE h...

In this study, [Co/Ni]2/PtMn thin films with different PtMn thicknesses (2.7 to 32.4 nm) were prepared on Si/SiO2 substrates. The post-deposition perpendicular magnetic field annealing (MFA) processes were carried out to modify the structures and magnetic properties. The MFA process also induced strong interlayer diffusion, rendering a less sharp i...

In this study, the addition of Y to CoFeB alloy can refine the grain size to study the magnetic, adhesion and optical properties of as-deposited and annealed CoFeB alloy. XRD analysis shows that CoFeB(110) has a BCC CoFeB (110) nanocrystalline structure with a thickness of 10–50 nm under four heat-treatment conditions, and a CoFeB(110) peak at 44°...

The structure, magnetic properties, optical properties and adhesion efficiency of CoFeBY films were studied. Co40Fe40B10Y10 alloy was sputtered onto Si (100) with a thickness of 10–50 nm, and then annealed at room temperature, 100 °C, 200 °C and 300 °C for 1 h. X-ray diffraction (XRD) showed that the CoFeBY films deposited at room temperature are a...

The understanding of the characteristics of a magnetic layer in a different environment is crucial for any spintronics application. Before practical applications, thorough scrutiny of such devices is compulsory. Here we study such a potential Hall device of MgO-capped Hf/GdFeCo bilayer (FeCo-rich) for magnetization relaxation around nucleation fiel...

The understanding of the characteristics of a magnetic layer in a different environment is crucial for any spintronics application. Before practical applications, thorough scrutiny of such devices is compulsory. Here we study such a potential Hall device of MgO-capped Hf/GdFeCo bilayer (FeCo-rich) for magnetization relaxation around nucleation fiel...

In this study, a 10–50 nm Co32Fe30W38 alloy thin film sputtered on glass substrates was annealed at different temperatures for 1 h including room temperature (RT), 300, 350, and 400 °C. The structure, magnetic properties, surface energy, and optical properties of the Co32Fe30W38 alloy were studied. X-ray diffraction (XRD) patterns of the as-deposit...

We investigate the Hf/GdFeCo bilayer with the MgO cap layer for both rare earth (RE)-rich and transition metal (TM)-rich configurations of the ferrimagnetic sublattice in the presence of the perpendicular field. We study the coercivity using the anomalous Hall effect (AHE) technique by multiple measurements on the same sample. In the first set of m...

In this reported study, we looked into the magnetic properties of orthogonal magnetic tunnel junction (MTJ) structures using synthetic antiferromagnet (SAF) based on IrMn and PtMn. The free layer of the MTJ was prepared by Co40Fe40B20 with perpendicular magnetic anisotropy (PMA). The increase in the purity of sputtering Ar gas helped give a thinner...

In this study, a Co40Fe40W20 alloy was sputtered onto Si (100) with thicknesses () ranging from 18 to 90 nm, and the corresponding structure, magnetic properties, adhesive characteristics, and nanomechanical properties were investigated. X-ray diffraction (XRD) patterns of the Co40Fe40W20 films demonstrated a significant crystalline body-centered c...

We report on a theoretical study of thermal magnetization switching induced by nanosecond electric current pulse using Lagrangian formalism based on the Landau–Lifshitz–Gilbert equation. The parameters for modeling are obtained from the measurements of the anomalous Hall resistance at different probe currents. We obtain the switching diagrams, anal...

We present here a way to modulate the anisotropic magnetoresistance (AMR) by anomalous Hall signal and thus measure the domain wall (DW) motion velocity at near-coercivity. We study the magnetization relaxation at the constant field in the longitudinal (Rxx) Hall geometry. We observed asymmetric Rxx peaks that appear at the DW pinning fields. This...

We present here a way to modulate the anisotropic magnetoresistance (AMR) by anomalous Hall signal and thus measure the domain wall (DW) motion velocity at near-coercivity. We study the magnetization relaxation at the constant field in the longitudinal (Rxx) Hall geometry. We observed asymmetric Rxx peaks that appear at the DW pinning fields. This...

X-ray diffraction patterns demonstrated a significant nanocrystalline body-centred cubic CoFe (110) structure when the thickness was between 60 and 90 nm, and displayed an amorphous status when the thickness was from 18 to 42 nm. The saturation magnetization (Ms) and low-frequency alternate-current magnetic susceptibility (χac) revealed a thickness...

Experimental studies of the anomalous Hall effect are performed for thin-film Ta/Tb−Fe−Co over a wide range of temperatures and magnetic fields up to 3 T. Far from the compensation temperature ($T_{M}$ = 277 K), the field dependence has a conventional shape of a single hysteresis loop; just below the compensation point, the dependence is anomalous...

In this study, the interfacial PMA in (Ta or Hf)/TbFeCo/MgO/Ta structures are investigated and the effectiveness of two kinds of heavy-metal Hf and Ta underlayers are explored. The PMA of TbFeCo is found to critically rely on several aspects like Tb-concentration (Tb sputtering power), underlayer material (Ta/Hf), annealing temperature and heating...

When B and V are added to CoFe material, the mechanical strength and spin tunneling polarization of a CoFe alloy can be improved and enhanced by the high tunneling magnetoresistance (TMR) ratio. Based on these reasons, it is worthwhile investigating Co40Fe40V10B10 films. In this work, X-ray diffraction (XRD) showed that Co40Fe40V10B10 thin films ha...

Among various perpendicularly anisotropic magnetic materials, amorphous rare earth-transition metal RE-TM alloys have attracted much interest due to the advantages of tunable magnetic properties and suitable perpendicular magnetic anisotropy (PMA) strength. In this study, the magnetic properties of the Ta/TbFeCo/MgO structure with various Tb-conten...

We study the effect of inserting Fe and FeCo thin layers between the MgO and the magnetic layer in the TbFeCo-based perpendicular magnetic tunnel junction (pMTJ). Different half and full structure MTJ were prepared and thin layers of Fe and FeCo were inserted between the MgO-TbFeCo interface. It is observed that in both the reference and free layer...

This study investigated the structure and magnetic properties of Co40Fe40V20 thin films with a thicknesses (tf) of 10 nm to 100 nm on a glass substrate. The X-ray diffraction (XRD) patterns of the CoFeV films demonstrated a significant crystalline body-centered cubic (BCC) CoFe (110) structure when the thickness was between 60 and 100 nm, and an am...

Experimental studies of anomalous Hall effect are performed for thin filmed Ta/TbFeCo in a wide range of temperatures and magnetic fields up to 3 T. While far from the compensation temperature (TM=277 K) the field dependence has a conventional shape of a single hysteresis loop, just below the compensation point the dependence is anomalous having th...

The control of magnetic properties by electric current in nanoscale devices is critical for advanced applications of spintronics. Here, we study the anomalous Hall effect in amorphous TbFeCo/Ta/MgO structure for various dc sense currents using the Hall bar pattern. The aspect ratio of the Hall bar structure is changed by simply interchanging the cu...

Antiferromagnetic magnetization dynamics is more effective than ferromagnetic magnetization; however, it is extremely complex. Rare earth (RE) ferrimagnets, on the other hand, have tunable magnetization with associated negative exchange interaction in sublattices. Here, we study different RE-Fe ferrimagnets while changing the RE-content. We obtain...

The superconductor (SC)/ferromagnetic (FM) systems have shown tremendous attention due to their amazing phenomena at the SC/FM interfaces such as the inverse proximity effect, triplet superconducting pair generation and the non-dissipation spintronics, which exhibit a great potential on scientific development and applications. To explore these uniq...

Interlayer dipolar coupling is an important aspect in magnetic switching devices from the application point of view. Here, we identify various sources affecting the interlayer dipolar coupling in CoFeB-based perpendicular magnetic tunnel junctions (pMTJs). By changing the MgO tunnel barrier layer thickness, we show that it plays a crucial role in c...

MnBi is a promising ferromagnetic material for applications at elevated temperatures due to its high Curie temperature, sizable magnetocrystalline anisotropy, and increasing coercivity with temperature. However, fabrication of MnBi thin films with ferromagnetic low-temperature phase (LTP) is conventionally difficult due to the peritectic Mn-Bi reac...

The following structures are deposited under the conditions (a) glass/Ru(X nm)/Co60Fe20V20(5 nm) and (b) glass/Ta(Y nm)/Co60Fe20V20(5 nm) at room temperature (RT), where X and Y is from 5 nm to 10 nm. X-ray diffraction (XRD) patterns of glass/Ru(X nm)/Co60Fe20V20(5 nm) and glass/Ta(Y nm)/Co60Fe20V20(5 nm) reveal a weak crystallization at peak β-(20...

Co60Fe20V20thin films with thicknesses ranging from 3 to 13 nm were sputtered onto a Si(100) substrate at room temperature (RT). Captured selected-Area diffraction patterns (SADs) and highresolution cross-sectional transmission electron microscopy (HR X-TEM) images revealed that the microstructures of the Co60Fe20V20 thin films were amorphous. The...

The following structures are deposited under the conditions stated: (a) glass/Ru (X nm)/Co60Fe20V20(5 nm) and (b) glass/Ta(Y nm)/Co60Fe20V20(5 nm) at room temperature (RT), where each of X and Y is from 5 nm to 10 nm. The hysteresis loop of glass/Ru (X nm)/Co60Fe20V20(5 nm) and glass/Ta(Y nm)/Co60Fe20V20(5 nm) presents in-plane easy-axis magnetic a...

In this study, the maximum alternating current (AC) magnetic susceptibility (χac) and optimal resonance frequency (fres) of (a) glass/Ru (X nm)/Co60Fe20V20(5 nm) and (b) glass/Ta(Y nm)/Co60Fe20V20(5 nm) films at room temperature (RT) were investigated through low-frequency AC magnetic susceptibility (χac) measurement, where X and Y each ranged from...

In this study, 3–13-nm-thick CoFeV thin films were sputtered onto a glass substrate at room temperature (RT), and their structure and electrical characteristics were examined. X-ray diffraction (XRD) and high-resolution cross-sectional transmission electron microscopy (HR X-TEM) were utilized to determine the structure and microstructure of the thi...

In this study, Co60Fe20V20 films were sputtered onto a glass substrate with various thicknesses from 3 to 13 nm at room temperature (RT). The microstructure and low-frequency alternative-current magnetic susceptibility (χac) were examined. Selected-area-diffraction (SAD) patterns and highresolution cross-sectional transmission electron microscopy (...

We present the study of the dynamic properties of CoFeB (CFB) based magnetic tunnel junctions (MTJ) by Brillouin light scattering spectroscopy and micro-strip ferromagnetic resonance technique as well as magnetoresistance measurements. Two different MTJs: single and double barrier systems have been investigated. The dynamic studies revealed mostly...

 FMR and BLS metrology of the magnetic material parameters in CoFeB-based MTJs  Double barrier MTJs with nanoparticles (npMTJs) are more suitable for applications  Addition of Fe nanoparticles : optimal TMR ratio increased by up to 111%

We report low-frequency electrical resistance noise of Co40Fe40B20/MgO/Co20Fe60B20-based magnetic tunnel junction field sensors with reference and sensing layer magnetization directions along the out-of-plane and in-plane directions, respectively. The devices are fabricated using the sputter deposition and conventional lithography techniques with a...

The impact of a non-magnetic Ta spacer layer on the perpendicular magnetic anisotropy (PMA) of composite magnetic structures constituted by ultra-thin Co/Pd multilayers (MLs) and MgO/CoFeB was studied. Composite structures lacking a Ta layer present in-plane magnetic anisotropy. The strong perpendicular anisotropy observed in sole Co/Pd MLs is not...

Here, we investigate the size effect of perpendicular-anisotropic magnetic tunnel junction (MTJ) devices embedded with iron nanoparticles. A sputtering system in conjunction with post-annealing process is employed to prepare the sheet film and, standard lithography followed by etching technique is used to fabricate the micron to submicron MTJ devic...

In this paper, we attempt the theoretical modeling of the magnetic tunnel junctions with embedded magnetic and nonmagnetic nanoparticles (NPs). A few abnormal tunnel magnetoresistance (TMR) effects, observed in related experiments, can be easily simulated within our model: we found, that the suppressed TMR magnitudes and the TMR sign-reversing effe...

In a magnetic tunnel junction (MTJ) device, the potential barrier height of the barrier layer, in presence of a bias voltage or an external magnetic field, can be affected by defects present in the barrier layer or at the barrier layer/ferromagnetic (FM) layer interfaces of the device. The defects may have structural as well as magnetic origin. Flu...

A magnetic tunnel junction (MTJ) with orthogonal magnetic anisotropy and consisting of Ta X/Co40Fe40B20 1.2 (reference)/MgO 2.0/Co20Fe60B20 2.3 (sensing)/Ta 5/Ru 5 (thickness in nanometers), where X ranges from 15 to 30, is proposed and investigated in response to the demand for out-of-plane field sensors. The reference layer with perpendicular mag...

In this study, NiFe thin films were deposited on a glass substrate at room temperature (RT) or postannealed at 150 and 250 °C for 1 h; the Ni80Fe20 films were 300-1500 Å thick. The microstructure, surface energy, and average contact angle properties of the NiFe thin films were investigated. X-ray diffraction (XRD) results demonstrated that the NiFe...

Double barrier Magnetic tunnel junction (DBMTJ) is an attractive issue in the field of spintronics due to potential applications, such as spin diode [1], magnetic field sensor [2], and non-volatile spin-transfer-torque magnetic random access memories [3]. Essentially, the DB structures give rise to a high spin filtering efficiency, thus not only en...

We present a theoretical simulation to calculate the tunnel magnetoresistance (TMR) in magnetic tunnel junction with embedded nano-particles (npMTJ). The simulation is done in the range of coherent electron tunneling model through the insulating layer with embedded magnetic and non-magnetic nano-particles (NPs). We consider two conduction channels...

In this paper, we report the electric and magnetic effects after inserting Fe nanoparticles into the MgO layer of a Ta(25)/Co₂₀Fe₆₀B₂₀(1.3)/MgO(1)/Fe(x)/MgO(1)/Co₄₀Fe₄₀B₂₀(2.2)/Ta(5) structure. The samples were annealed at 300 °C without external magnetic field. Temperature dependenc...

The transport properties of stacked CoFeB (1.86)/MgO (0.2)/Fe-nanoparticles (${rm t}_{rm Fe}$)/MgO (0.5)/CoFeB(0.6) double barrier magnetic tunnel junctions have been characterized. In this investigation, stacked film is prepared by magnetron sputter system, annealed at 250$^{circ}$, and patterned into a micron-scale device using standard electron...

Edge effect plays a major role on magnetic properties in permalloy microstructures. To perform high dynamic range, the meander line has been used in giant magnetoresistance (GMR) sensor for increasing the sensor active area. In this paper, we fabricated GMR sensors with various edge structures by using a photolithography and e-beam evaporation syst...

Presents the welcome message from the conference proceedings. The issue includes 123 papers.

We studied the effect of a thin Ta layer on the perpendicular magnetic anisotropy (PMA) of composite FM1/Ta/FM2 magnetic structures, where FM1 represents the subsystem MgO/CoFeB, and FM2 denotes a [Co/Pd]6 multilayer. The stack without Ta spacer layer shows no PMA. Once a Ta layer is inserted between the thin CoFeB layer and the [Co/Pd]6 multilayer...

In A method for measuring a dimensionless coupling constant of a magnetic structure includes the following steps. A step of applying an external vertical magnetic field is performed for enabling magnetic moments of a RE-TM (Rare Earth-Transition metal) alloy magnetic layer of the magnetic structure to be vertical and saturated. A step of measuring...

Magnetizations dynamic effect in low current read disturb region is studied both experimentally and theoretically. Dramatic read error rate reduction through read pulse width control is theoretically predicted and experimentally observed. The strong dependence of read error rate upon pulse width contrasts conventional energy barrier approach and ca...

In this study, we report the effects of deposition rate and composition of CoFeB on the magnetic properties of CoFeB/MgO/CoFeB structures. We found that the asymmetry exists not only in different deposition stack sequences (bottom structure Ta/CoFeB/MgO and top structure MgO/CoFeB/Ta), but also in different compositions of CoFeB. Co40Fe40B20 is mor...

The interplay between interlayer coupling and exchange bias coupling in [NiFe/Mn] multilayerbased thin films was investigated by using ion-beam bombardment during deposition to control the configurations from superlattice to nanocomposite or hybrid-structured thin films. Results showed that well-defined interfaces in the superlattice [NiFe/Mn] thin...

We fabricated MgO-based perpendicular magnetic tunnel junctions (p-MTJ) with Ta/CoFeB magnetic electrodes. Synthetic antiferromagnetic (SAF) pinned layers with perpendicular magnetic anisotropy (PMA) were included into the p-MTJs by using two Co/Pd multilayers (MLs) separated by a thin Ru spacer layer. The MTJs stack has the structure bottom contac...

We present an alternative method of spin-transfer-induced magnetization switching for magnetic tunnel junctions (MTJs) using a conductive atomic force microscope (CAFM) with pulsed current. The nominal MTJ cells' dimensions were 200 × 400 nm2. The AFM probes were coated with a Pt layer via sputtering to withstand up to several milliamperes. The pul...

We have investigated the exchange coupling between a bottom FePt thin film layer capped with different Mn-oxides. Results have shown that the magnetization reversal of the soft FePt layer is influenced strongly by the capped Mn-oxide layer (Mn, MnO, and Mn3O4), as revealed by the enhanced coercivities. Typical temperature dependent magnetization be...

In this study, we investigated the exchange bias (coupling) effects in CoFe/(Co,Fe)O bilayers by using different single crystal substrates of MgO(100) and MgO(110) and Ar ion-beam bombardment on the surface of the bottom antiferromagnet (Co,Fe)O layer before capping with ferromagnet CoFe. In the CoFe/(Co,Fe)O/MgO(110) bilayer, above the irreversibi...

In this study, we report the effects of electrode and annealing on the magnetic properties of CoFeB-MgO-CoFeB-TbFeCo structures. The samples of structure bottom electrode/Co20Fe60B20(x nm)/MgO(1)/Co20Fe60B20(0 or 1 nm)/Tb23(Fe80Co20)77(5 nm)/top electrode were deposited on SiO2 substrates at room temperature. The structures were then annealed at th...

The coercivity and exchange bias field of ferro-/antiferromagnetic Co90Fe10/CoFe-oxide bilayers were studied as function of the surface morphology of the bottom CoFe-oxide layer. The CoFe-oxide surface structure was varied systematically by low energy (0--70 V) Argon ion-beam bombardment before subsequent deposition of the Co90Fe10 layer. Transmiss...

The coercivity and exchange bias field of ferro-/antiferromagnetic Co90Fe10/CoFe-oxide bilayers were studied as function of the surface morphology of the bottom CoFe-oxide layer. The CoFe-oxide surface structure was varied systematically by low energy (0–70 V) Argon ion-beam bombardment before subsequent deposition of the Co90Fe10 layer. Transmissi...

This paper reviews the progress made over the last few years in understanding the development of perpendicular magnetic tunneling junctions (pMTJs). The material systems for making pMTJs, including rare-earth/transition metal alloys, L10-ordered (Co, Fe)–Pt alloys, Co/(Pd, Pt) multilayers, and CoFeB–MgO crystallized structures, are briefly introduc...

This paper reports the results obtained using TbFe and FeCo alloys as the electrodes of MgO-based perpendicular magnetic tunnel junctions (pMTJs). Without annealing treatment, the as-deposited structure showed MgO (001) crystalline texture. The tunnel magnetoresistance (TMR) ratio measured from the patterned cell of size 3 6 m was 9.5% at room temp...

The perpendicular magnetic anisotropy of a series of top MgO/CoFeB/Ta layers is studied. Similar to the bottom Ta/CoFeB/MgO structure, the critical thickness of CoFeB is limited in a range of 1.1–1.7 nm. However, the cap layer shows much sensitive effect. Not only the type of material is crucial, but the thickness of the cap layer also affects the...

This study reports an alternative method for measuring the magnetoresistance of unpatterned magnetic tunnel junctions similar to the current-in-plane tunneling (CIPT) method. Instead of using microprobes, a series of point contacts with different spacings are coated on the top surface of the junctions and R-H loops at various spacings are then meas...

This paper reports the micromagnetic simulations of spin-wave modes excited by spin-transfer torque for an elliptical nanomagnet sized 178 × 133 × 2.1 nm³. Through power spectral analysis we discovered that, for the collinear case, the excited spin-wave mode exhibits the same spatial symmetry as the initial ground state. The additional a...

Spin-transfer torque (STT) enables magnetization switching by passing a spin-polarized current through nanostructures such as spin-valves or magnetic tunnel junctions (MTJs). The required switching current depends on the pulse width which is related to the feature of switching modes. In this work the STT-induced switching processes for several nano...

A series of hysteresis loops with off-axial external magnetic fields have been measured to identify magnetization reversal properties as well as coupling effects in magnetic tunnel junctions (MTJs). MTJ films, consisting of a synthetic artificial antiferromagnetic pinned layer of CoFeB/Ru/CoFe/IrMn, were patterned into an elliptical cell array with...

In this paper, we present a direct method to analyze the mechanism of magnetic domain reversal for a series of amorphous Dyx(FeCo) 1-x magnetic thin films and whereby we obtained the distributions of the coercivities and interaction fields from 90,000 measurements of the microhysteresis loops. The standard deviations of the coercivity and the inter...

Magneto-impedance (MI) of a double-barrier MgO magnetic tunnel junction (DMTJ) is measured as a function of frequency (20 Hz–3 MHz) and DC bias (−1 to 1 V) under magnetic parallel and antiparallel states. A strong nonlinear effect is observed at all frequencies and the MI changes from positive to negative at the relaxation frequency ∼1/RC. A freque...

The perpendicular magnetic tunnel junctions of structure Si/Ti(10 nm)/TbFeCo(22 nm)/CoFeB(2 nm)/MgO(1 nm)/CoFeB(1 nm)/TbFeCo(3 nm)/Ti(10 nm) were deposited on SiNx substrates at room temperature with various Tb contents. The samples were then annealed at different temperatures ranging from 150 to 350 ° C . We found that the magnetic tunnel junction...

We fabricated a series of perpendicularly magnetic tunnel junctions (pMTJs) of the structures Si/Ti/GdCoFe/Mg(0 or 0.4nm)/MgO(x)/Mg(0 or 0.4nm)/TbCoFe/Ti with various MgO barrier thicknesses. The effect of inserting Mg layers was investigated through high resolution transmission electron microscopy and hysteresis loop measurement. Experimental resu...

Perpendicular ultrathin RE-TM films with thickness 3 nm were investigated for potential use as free layers of perpendicular magnetic tunnel junctions. The free layer thickness should be as thin as possible to reduce spin-transfer switching current density while maintaining adequate thermal stability. Using Ti or Al as under- and over-layers, we fou...